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Qiong Huang,1,2 Li Luo,1 Bing-qing Xia,1 Ding-Jun Zhang,1 Chen-di Dong,1 Jiao-wang Tan,1,3 Li-zhe Fu,4 Fang Tang,4 Xian-long Zhang,1 Bei-ni Lao,1 Yan-min Xu,1 Hui-fen Chen,1 Xu-sheng Liu,5 Yi-fan Wu5 1The Second Clinical College, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, People’s Republic of China; 2Blood Purification Center, Heyuan Hospital of Traditional Chinese Medicine, Heyuan, Guangdong, People’s Republic of China; 3Renal Division, Beijing University of Traditional Chinese Medicine Shenzhen Hospital, Shenzhen, Guangdong, People’s Republic of China; 4Chronic Disease Management Outpatient Department, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine (Guangdong Provincial Hospital of Chinese Medicine), Guangzhou, Guangdong, People’s Republic of China; 5Renal Division, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine (Guangdong Provincial Hospital of Chinese Medicine), Guangzhou, Guangdong, People’s Republic of ChinaCorrespondence: Yi-fan WuRenal Division, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine (Guangdong Provincial Hospital of Chinese Medicine), No. 111 Dade Road, Yuexiu District, Guangzhou 510120, People’s Republic of ChinaTel/ Fax +86-20-81887233Email wuyifan007@gzucm.edu.cnPurpose: This study aimed to simplify the version-1 Chinese and Western medication adherence scale for patients with chronic kidney disease (CKD) to a version-2 scale using item response theory (IRT) analyses, and to further evaluate the performance of the version-2 scale.Materials and Methods: Firstly, we refined the version-1 scale using IRT analyses to examine the discrimination parameter (a), difficulty parameter (b) and maximum information function peak (Imax). The final scale refinement from version-1 to version-2 scale was also decided upon clinical considerations. Secondly, we analyzed the reliability and validity of version-2 scale using classical test theory (CTT), as well as difficulty, discrimination and Imax of version-1 and version-2 scale using IRT in order to conduct scale evaluation.Results: For scale refinement, the 26-item version-1 scale was reduced to a 15-item version-2 scale after IRT analyses. For scale evaluation using CTT, internal consistency reliability (total Cronbach α = 0.842) and test-rest reliability (r = 0.909) of version-2 scale were desirable. Content validity indicated 3 components of knowledge, belief and behaviors. We found meritorious construct validity with 3 detected components as the same construct of medication knowledge (items 1– 9), medication behavior (items 13– 15), and medication belief (items 10– 12) based upon exploratory factor analysis. The correlation between the version-2 scale and Morisky, Green and Levine scale (MGL scale) was weak (Pearson coefficient = 0.349). For scale evaluation with IRT, the findings showed enhanced discrimination and decreased difficulty of most retained items (items 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15), decreased Imax of items 1, 2, 3, 4, 6, 11, 14, as well as increased Imax of items 5, 7, 8, 9, 10, 12, 13, 14, 15 in the version-2 scale than in the version-1 scale.Conclusion: The original Chinese and Western medication adherence scale was refined to a 15-item version-2 scale after IRT analyses. The scale evaluation using CTT and IRT showed the version-2 scale had the desirable reliability, validity, discrimination, difficulty, and information providedoverall. Therefore, the version-2 scale is clinically feasible to assess the medication adherence of CKD patients.Keywords: chronic kidney disease, traditional Chinese medicine, medication adherence scale, item response theory